1. Field of the Invention
The present invention is directed to an ambient feed spheridization process for producing prills of ammonium dinitramide ("ADN"). More particularly, the present process produces at least essentially solid spherically-shaped particles ("prills") of thermally-stabilized ammonium dinitramide, with the capability of tailoring the relative modality, e.g., particle size distribution, of the prills. The present invention further relates to the prilled particles, and energetic formulations containing the prills, such as, for example, solid propellants and explosives.
2. Description of the Related Art
Ammonium dinitramide offers the promise of desirable oxidizer properties, including relatively high density, high oxygen content, and an acceptable heat of formation, while avoiding the environmental hazards associated with halogen-containing, and in particular chlorine-containing, oxidizers.
Unfortunately, the promise of this relatively new oxidizer has not been fully realized, since ADN also suffers from deleterious attributes, including hygroscopicity, poor morphology (planks), and low thermal stability. With regard to this last attribute, ADN is markedly less thermally stable than ammonium nitrate, which is a well known and commonly used oxidizer. Indeed, the initial onset of ADN decomposition to ammonium nitrate and N.sub.2 O can be observed at as relatively a low temperature as approximately 90-92.degree. C.
Over the last several years, efforts have focused on methods of preparing ADN and the use of ADN in propellant formulations and other formulations. These recent processes include those disclosed in U.S. Pat. No. 5,198,204, U.S. Pat. No. 5,415,852, and U.S. Pat. No. 5,316,749, the complete disclosures of which are incorporated herein by reference.
Despite the advancements provided by the processes disclosed in these patents, there remains a need for a commercially practical process for producing ADN prills which minimizes or eliminates the detrimental attributes of the oxidizer.